The present invention relates generally to ignitions systems, and more particularly to ignition coils for developing a spark firing voltage that is applied to one or more spark plugs of an internal combustion engine.
Ignition coils are known for use in connection with an internal combustion engine such as an automobile engine, and which include a primary winding, a secondary winding, and a magnetic circuit. The magnetic circuit conventionally may include a cylindrical-shaped, central core extending along an axis, located radially inwardly of the primary and secondary windings and magnetically coupled thereto. One end of the secondary winding is conventionally configured to produce a relatively high voltage when a primary current through the primary winding is interrupted. The high voltage end is coupled to a spark plug, as known, that is arranged to generate a discharge spark responsive to the high voltage. The discharge spark causes a break down of the spark gap of the spark plug.
As ignition coils are located closer to the spark plug, a high voltage transient occurs at the breakdown of the spark gap. This high voltage transient causes a wire to wire short in the secondary winding of the ignition coil, which results in a reduction of output and in some cases, irreparable damage to the ignition coil. Accordingly, the problem of wire to wire transients occurs as a result of the gap breakdown.
Systems are being developed that use a standard ignition system to break down the gap and further include a secondary power source to provide a high power discharge. One approach taken in the art is disclosed in U.S. Pat. No. 6,321,733 (""733 Patent) and U.S. Pat. No. 5,704,321 both issued to Suckewer et al. The ""733 Patent discloses a conventional ignition system which provides the high voltage necessary to break down the gap of the spark plug, in combination with the secondary power source that includes a voltage source and other circuitry to provide high power input to the spark gap once the conducting path there across (i.e., the plasma) has been established by the standard ignition system. A low resistance must be used between the high power source and the spark gap or a significant amount of energy would be lost. Accordingly, due to the low resistance, these systems require significant electrical shielding to operate without RFI. This shielding can reduce RFI, but does nothing to protect the secondary winding of the ignition coil from problems associated with wire to wire shorts.
Accordingly, there is a need for an ignition apparatus that minimizes or eliminates one or more of the problems set forth above.
It is an object of the present invention to minimize or eliminate one or more of the problems set forth in the Background. An ignition system according to the present invention overcomes shortcomings of a conventional ignition system of the type having (i) a conventional ignition coil to breakdown the spark gap and (ii) a secondary power source to sustain discharge after breakdown by including an impedance device in series with an output of the ignition coil (i.e., the secondary winding). An ignition system for use with a spark plug in an internal combustion engine and includes an ignition apparatus for producing a breakdown voltage on a first output thereof configured to breakdown a spark gap of the spark plug, a power source having a second output configured for connection to the spark plug, the source being further configured to provide power to the spark gap to sustain discharge phase after said gap breakdown, an impedance having first and second terminals coupled between the first and second outputs, the impedance having electrical characteristic configured to allow application of said breakdown voltage and suppress high voltage transient current on the secondary winding of the ignition apparatus.